1. Field of the Invention
The invention is based on a method and a device for operating a synchronous machine in accordance with the preamble of claims 1 and 2.
2. Discussion of Background
In the preambles of claims 1 and 2, the invention refers to a background which is known from the ASEA Journal 1976, Vol. 4, pages 75-80. In this journal, a static frequency converter, the link voltage of which is used for exciting the rotor windings, is used for starting pump turbine units with synchronous machines. Above a frequency of 5 Hz, the system switches from self-commutation with resonant-circuit control to load-controlled commutation with the aid of the voltage generated by the motor. At about 15% of the rated speed, the water is pushed down in the pump turbine so that the runner rotates in air during the remaining run-up. The plant is provided with an integrated protection device for detecting and signalling internal disturbances such as overvoltages and ground faults. There is an electronic pulse inhibitor as protection against overcurrents.
German Offenlegungsschrift 21 10 747 discloses a comparable background for starting gas turbines or pumped-storage units.
There is no provision for redundantly using the static converters of the frequency converters in a fault case.
Additional reference relating to the relevant background is made to the house journal of the Swiss firm BBC Brown, Boveri & Company, Baden, publication No.: CH-E 2.0340.0 E, title: Standardized Starting Equipment, January 1979, pages 1-8, from which it is known to start synchronous machines, which can be used, for example, in conjunction with gas turbines, pumped-storage plants and synchronous compensators, by means of a static frequency converter.